This invention relates to communication systems in general, and particularly to a communication system in which a radio can be registered with the system. Use of two-way radios offers advantages over the use of wired telephones, as for example, in a building or other site. The use of such a radio or personal communicator allows the user to be in constant telephone communication regardless of his location away from a fixed telephone. However, when the user leaves the building or site, communication with the user via the system is typically not possible. Where a telephone or other call is received at the site, while the user is off-site, it would be desirable to provide a method of advising the user of receipt of the call.